Etymology

A native formation on agayn + adverbial -es from the OE str. masc. and neut. gen. ending.
 

PGmc Ancestor

*gagni-

Proposed ON Etymon (OIcel representative)

(í) gegn 'in opposition, against, in return'
(ONP gegn (1) (sb.))

Other Scandinavian Reflexes

Far ígen, Icel gegn, Dan igen, OSw gen

OE Cognate

on-gegn, on-gēan  'against'; cp. ongegnes 'against'

Phonological and morphological markers

absence of palatalization of */ɡ/

Summary category

A1*c

Attestation

As with agayn, spellings reliably representing /ɡ/ are rare in the South and West until c. 1400, but are normal in the Chaucer citations in MED and become increasingly frequent in southern texts thereafter.

Occurrences in the Gersum Corpus

Pe 79; Cl 611, 1711; WA 170, 473, 953, etc.

Bibliography

MED ayẹ̄n(e)s (prep.) , OED against (prep., conj., adv. and n.) , HTOED ; Bj. 151, de Vries gegn, Mag. gegn (2), Orel *ʒaʒnē, AEW gegn (2)